1. Field of the Invention
The invention relates to an illumination device or unit for use in vehicular lamps, game machines, decorative illuminations, etc. More particularly, it relates to an illumination device or unit of the type that introduces light into a light guide having a free shape, such as a linear shape, a curved shape, an annular shape, etc., through at least one end of the light guide.
2. Description of the Related Art
FIG. 6 is an example of the related art showing a method of coupling a light guide 101 to a light source (light emitting diode 102) that emits light that is led to the light guide 101. The light guide 101 is inserted through an open end provided at a guide portion 104 of a body 103 and fixed by a screw 105. A collimator lens 107 and a condenser lens 108 are attached to a support member 109, which is inserted into a cylinder 106 of the body 103 and fixed by a fastening screw 110.
The light emitting diode 102 serving as the light source is mounted on an aluminum-based printed circuit board 111, which is attached to a base 112 by a resinous screw 113. An electric wire 114 for supplying power to the light emitting diode 102 is inserted through the outer bottom of the base 112 and connected by soldering to a mounting surface of the aluminum-based printed circuit board 111.
The base 112 (to which the aluminum-based printed circuit board 111 with the light emitting diode 102 mounted thereon is attached), the support member 109 (to which the collimator lens 107 and the condenser lens 108 are attached), and the body 103 (to which the light guide 101 is attached), can be coupled together by engaging a male threaded portion 115, which is formed on the outer rim around an open end of the base 112, with a female threaded portion 116, which is formed on the inner wall around an open end of the cylinder 106 of the body 103.
In the illumination device 200 thus configured, the light emitted from the light emitting diode 102 is converted at the collimator lens 107 into an almost collimated light, which advances to the condenser lens 108. The collimated light is condensed at the condenser lens 108 having a focus in the vicinity of an incident end surface 117 of the light guide 101. The condensed light is introduced through the incident end surface 117 of the light guide 101 into the light guide 101 and guided inside the light guide 101 to an exit end surface 118. It is finally externally radiated (to the atmosphere) from the exit end surface 118 (see, for example, Japanese Patent Application Publication No. JP-A 2004-45192).
The above-described conventional illumination device is assembled with screw fixtures at three locations and a thread engagement at one location. The screw fixtures at three locations include the following. The aluminum-based printed circuit board with the light emitting diode mounted thereon is fixed to the base at a first location. The support member with the collimator lens and the condenser lens attached thereto is fixed to the cylinder of the body at another location. The light guide is fixed to the open end provided at the guide portion of the body at a yet another location.
The thread engagement is also found in the coupling among the base (to which the aluminum-based printed circuit board with the light emitting diode mounted thereon is attached), the support member (to which the collimator lens and the condenser lens are attached), and the body (to which the light guide is attached).
Accordingly, on assembling the illumination device thus configured, an increase in the number of assembly steps associated with the steps for screw fixtures at three locations and the step for thread engagement at one location results in a reduction in yield and accordingly boosts production costs.
Further, no structure or device is provided for positioning the incident end surface of the light guide. Accordingly, when the light guide is inserted and fixed in the open end provided at the guide portion of the body, the incident end surface of the light guide varies in position on a product by product basis. As a result, the illumination pattern emitted from the light guide varies among products.
The invention has been devised in consideration of the above and other problems. In accordance with an aspect of the invention, an illumination device can be capable of achieving easy operation and maintenance for coupling between a light source and a light guide. The illumination device can also be capable of precisely reproducing a positional relation between the light source and a light incident surface of the light guide, and achieving less variation in illumination pattern among products.